Solar electric power plant and an improved thermal collector of solar energy

Abstract

A thermal collector of solar energy includes an elemental semiconductor material to absorb a substantial portion of the energy of solar radiation that is incident upon the material. At longer wavelengths, such material reradiates absorbed energy at a substantially reduced rate, whereby the efficiency of energy collection at high temperatures is improved. In a solar electric power plant collected heat is transferred from such collectors to a motive fluid, which drives a turbine-generator. The high operating temperature of the energy-absorbing material permits efficient conversion of the collected energy to electrical energy, while a required number of solar collectors is correspondingly reduced by the improved collection efficiency.

I claim: 
     
       1. A thermal collector of solar energy that is adapted to delivery collected energy to a heat using apparatus, comprising, first means for transmitting solar radiation,   second means for supporting a finely divided semiconductor material in relation to said first means to expose the semiconductor material to the transmitted radiation, whereby the semiconductor material absorbs at least a portion of the energy of the transmitted radiation and is heated by the absorbed energy, and   third means for transferring heat from the semiconductor material to the heat using apparatus.   
     
     
       2. A thermal collector according to claim 1 wherein said second means includes a mesh having opening sufficiently small to carry the finely divided semiconductor material, said mesh being oriented to expose the semiconductor material to the transmitted radiation, and said third means includes, means for passing a coolant gas through said mesh in heat transfer relation with the semiconductor material, whereby the coolant gas acquires heat from the semiconductor material.   
     
     
       3. A thermal collector according to claim 1 wherein said second means includes, a thermally conductive binder to hold the finely divided semiconductor material dispersed therethrough, and   a thermally conductive backing bearing said binder on at least one of its surfaces, said backing being oriented to expose said binder to the transmitted radiation, whereby heat of absorbed energy flows through said binder and through said backing, and said third means includes,   means for transferring heat from said backing to the heat using apparatus.   
     
     
       4. A thermal collector according to claim 3 wherein said binder is substantially transparent to radiation of wavelength less than 20 microns. 
     
     
       5. A thermal collector according to claim 1 wherein said second means includes, a sintered stratum of the finely divided semiconductor material,   a thermally conductive backing, and   means for holding said stratum to at least one surface of said backing, said backing being oriented to expose said stratum to the transmitted radiation, and said holding means being thermally conductive and in thermal communication with said stratum and said backing, whereby heat flows from said stratum through said holding means and said backing, and said third means includes,   means for transferring heat from said backing to the heat using apparatus.   
     
     
       6. A thermal collector according to claim 1 wherein the semiconductor material is an elemental semiconductor material. 
     
     
       7. A thermal collector according to claim 6 wherein the semiconductor material is annealed, high purity silicon. 
     
     
       8. A thermal collector of solar energy, comprising, a support,   a window to transmit solar radiation, said window being carried by said support,   a finely divided elemental semiconductor material to receive solar radiation and to absorb a substantial portion of the energy of the received radiation, said semiconductor material being heated by such absorbed energy, and   means for disposing said semiconductor material on said support to receive radiation that is transmitted by said window, and for transferring heat from the material to said support.   
     
     
       9. A thermal collector according to claim 8 wherein said means includes a thermally conductive binder, and the semiconductor material particles are disposed through the binder in a paint solution that is applied to said support. 
     
     
       10. A thermal collector according to claim 8 wherein said semiconductor material is formed into a sintered stratum, and said means includes a thermally conductive brazing material to hold the sintered stratum to said support. 
     
     
       11. A gas-cooled thermal collector of solar energy, comprising, a window to transmit solar radiation,   a support to carry said window,   a finely divided elemental semiconductor material to receive solar radiation and to absorb a substantial portion of the energy of the received radiation, said semiconductor material being heated by the absorbed energy,   means carried by said support for exposing said semiconductor material to solar radiation that is transmitted by said window, and   means for passing a flow of coolant gas in heat transfer relation with the semiconductor material particles, whereby the coolant gas acquires heat from the particles.   
     
     
       12. A thermal collector according to claim 11 wherein said semiconductor material is high purity, annealed silicon. 
     
     
       13. A solar electric power plant, comprising, a bed including a finely divided energy absorbing material to absorb at least a portion of the energy of solar radiation that is incident upon the material, said bed being pervious to a flow of coolant gas,   first means for supporting said bed and for transmitted solar radiation to the material of said bed,   second means connected to said first means for passing a flow of coolant gas in heat transfer relation with the material of said bed, whereby the gas is heated by the absorbed energy of solar radiation,   third means connected to said second means for deriving heat from the heated gas and generating stream from the derived heat,   a rotatable electric generator, and   a steam turbine connected to pass steam that is generated by said third means and rotatably coupled to drive said electric generator.   
     
     
       14. A power plant according to claim 13 wherein, and said bed includes a mesh to carry the finely divided material. 
     
     
       15. A power plant according to claim 13 wherein the energy-absorbing material is a finely divided semiconductor. 
     
     
       16. A power plant according to claim 13 wherein the energy-absorbing material is a finely divided elemental semiconductor. 
     
     
       17. A power plant according to claim 16 wherein the semiconductor material is substantially pure. 
     
     
       18. A power plant according to claim 16 wherein the finely divided semiconductor material is annealed. 
     
     
       19. A power plant according to claim 13 wherein said first means includes a glass window to transmit solar radiation to said bed. 
     
     
       20. A power plant according to claim 1 further comprising an insulating material applied to said first means to reduce a leakage heat flow from said first means to its environment. 
     
     
       21. A solar electric power plant, comprising, a body of finely divided elemental semiconductor material to receive solar radiation and absorb at least a portion of the energy of the received radiation, whereby the semiconductor material is heated by the absorbed energy,   a window to transmit solar radiation to said semiconductor body,   first means for supporting said window and for supporting said semiconductor body in relation to said window to expose said semiconductor body to the transmitted radiation,   second means for transferring heat from said semiconductor body to a motive fluid,   a turbine driven by the motive fluid, and   a rotatable electric generator driven by said turbine.   
     
     
       22. A power plant according to claim 21 wherein said second means includes, means for passing a flow of heat transfer fluid in heat transfer relation with said semiconductor body, whereby the heat transfer fluid acquires heat from the semiconductor material, and   means for transferring heat from the heated heat transfer fluid to the motive fluid.   
     
     
       23. A power plant according to claim 22 further comprising, means for governing the flow of motive fluid from said heat transfer means to said turbine, and   means for governing the flow of heat transfer fluid,   
     
     
       24. A power plant according to claim 22 wherein said first means includes a mesh having opening sufficiently small to carry said semiconductor body, and the heat transfer fluid is a coolant gas that passes through the mesh in thermal communication with the particles of the semiconductor material. 
     
     
       25. A power plant according to claim 24 where said mesh is disposed generally horizontally and carries said semiconductor body on its upper surfaces, and the coolant gas passes downwardly through said semiconductor body and said mesh. 
     
     
       26. A power plant according to claim 24 wherein said mesh is arranged to intersect the flow of coolant gas at least twice, the coolant gas being heated upon each passage through said mesh and said semiconductor material. 
     
     
       27. A power plant according to claim 21 wherein the semiconductor material is substantially pure silicon that is annealed after it is finely divided.